MASS STABILISATION MANUAL

ALLU 

MASS STABILISATION 

MANUAL

CONTENTS 

1.IDEACHIP AND RAMBOLL FINLAND – PROFESSIONAL SOLUTIONS 

FOR MASS STABILISATION 4 

2. MASS STABILISATION 9 

2.1 What is mass stabilisation? 9 

2.2 Applications of mass stabilisation 10 

2.3 Mass stabilisation versus other methods 11 

3. ALLU STABILISATION SYSTEM 14 

3.1 ALLU stabilisation machinery 14 

3.2 Technical information of the ALLU PM 14 

3.3 Technical information of the ALLU PF and ALLU DAC. 16 

3.4 Principles of ALLU mass stabilisation 17 

3.5 Cost Savings with the ALLU Stabilisation system 18 

4. MASS STABILISATION PROJECT IN A NUTSHELL 19 

5. FIELD SURVEYING 20 

5.1 Field tests and investigations 20 

5.2 Investigation methods 21 

5.3 Samples for the laboratory 21 

6. LABORATORY WORK 22 

6.1 Determination of soil properties 22 

6.2 Properties of the stabilised soft soils 23 

6.3 Stabilisation testing 24 

7. BINDERS 27 

7.1 Binder types 27 

7.2 Binders for different soil types 28 

7.3 Added sand in mass stabilisation 29 

7.4 Effects of binder quantity, curing time and preloading 29 

7.5 Effect on permeability 31 

7.6 Environmental acceptability 31 

8. DESIGNING 32 

8.1 Design requirements 32 

8.2 Loads 33 

8.3 Characteristic material values 33 

8.4 Design values 33 

8.5 Design 34 

9. STABILISATION WORK 36 

9.1 Stabilisation tests 36 

9.2 Mass stabilisation work 36 

9.3 Mass stabilisation log sheet 37 

Mass stabilisation 2005

CONTENTS 

10. QUALITY CONTROL 38 

10.1 Control procedure 38 

10.2 QC before construction 39 

10.3 QC during construction 40 

10.4 QC after construction 40 

10.5 Settlement monitoring 42 

10.6 Environmental acceptability 42 

11. FURTHER READING 42 

MASS STABILISATION CASES 44 

Note! This publication is intended for information purposes only, for those who are interested in 

mass stabilisation method. The background information provided in this report does not constitute 

a basis for design. Each site has unique soil conditions and functional requirements and therefore 

careful investigation and planning are always required before the stabilisation. Ideachip and Ramboll 

do not take any responsibility for misinterpretation or misuse of this text. 


IDEACHIP AND RAMBOLL FINLAND 

1. IDEACHIP AND RAMBOLL FINLAND – PROFESSIONAL 

SOLUTIONS FOR MASS STABILISATION 

Ideachip is a private Finnish company, which since 1985 has specialised in 

developing, manufacturing and selling products for environmental care, improvement 

of recycling methods and processing of various materials. Ideachip is an respected 

global supplier of accessories and appliances for both the environmental and earth 

construction fi elds. To date, Ideachip has delivered products to more than 40 countries 

throughout the world. 

Ideachip’s headquarters and factories are located in Finland. Currently, it maintains 

an active and skilled distributor network in more than 30 countries and it has delivered 

products to more than 40 countries all over the world. The main product lines of 

Ideachip are ALLU Screener Crushers and ALLU Stabilisation System. 

Ideachip has actively followed up with the changing requirements of the customers, 

developing new technical solutions and methods and its target is to be a pioneer of 

its branch. As an important part of the product development process Ideachip is continuously 

looking, together with its customers, for new application possibilities for ALLU 

products and develops new technically realisable solutions. 

ALLU Stabilisation System 

ALLU Stabilisation System is a new working method to increase the strength and dynamic 

stiffness of soft soil, in order to improve the engineering characteristics of soft 

soil and to remediate contaminated soil. 

Picture: ALLU Stabilisation system at work 

4 



The ALLU Stabilisation System consists of three components. The fi rst component is the ALLU 

PM Power Mix, a versatile hydraulic accessory for excavators. The second component is the ALLU 

PF Pressure Feeder, which injects the binder via hoses into the ground. The third component is 

the ALLU DAC Data Acquisition System, which measures, controls and provides data during the 

stabilisation project. 

The mass stabilisation method is a quick and cost effective solution to improve soft soils by 

mixing binder into clay, peat, mud or dredged sediments. The stabilisation method can also be 

used in treatment of contaminated soils, by encapsulating contaminants within the ground and 

preventing migration to the surrounding areas. It is a quick, cost effective, and environmentallyfriendly 

method in comparison with traditional methods of piling or soil replacement. 

With the continued goal of being a leader in its fi eld, Ideachip has actively adapted to the changing 

demands of its customers, developing new technical solutions and methods. As an important 

part of the product development process, Ideachip, together with its customers, is continuously 

searching for new application possibilities for ALLU products and developing new technically and 

economically feasible solutions. 

For more information: www.allu.net 

Finland 

Ideachip Oy (headquarters) 

P.O. Box 62, 15871 Hollola, 

FINLAND 

Tel: +358 3 882 140 

Fax: +358 3 882 1440 

Email: info@allu.net 

UK 

Ideachip UK Ltd. 

17 Victoria Road, 

Holywood Co. Down, 

N. IRELAND BT18 9BA 

Tel: +44 2890 428 822 

Fax: +44 2890 428 855 

Email: uk@allu.net 

China 

Ideachip China 

Victoria Plaza A-24E, 

1068 Xikang Road, 

200060 Shanghai, 

P.R. CHINA 

Tel: +86 21 6266 5999 

Germany 

Ideachip GmbH 

Opferfeldstraße 16-18, 

32130 Enger, 

GERMANY 

Tel: +49 5224 977 866 

Fax: +49 5224 977 867 

Email: deutschland@allu.net 

France 

Ideachip S.A.R.L 

28 Rue du Faubourg Madeleine, 

21200 Beaune, 

FRANCE 

Tel: +33 3 80 24 04 34 

Fax: +33 3 80 24 04 36 

Email: france@allu.net 

Fax: +86 21 6266 5777 

Email: china@allu.net 

Mass stabilisation 2005 

USA 

ALLU Group 

861 Main Street, Hackensack, 

New Jersey 07601, 

USA 

Toll Free: 800-939-ALLU (2558) 

Tel: +1 201 457 1003 

Fax: +1 201 457 3339 

Email: usa@allu.net 

Argentina 

Ideachip South America 

Cerrito 1070 Piso 7, 

C1010AAV Buenos Aires, 

ARGENTINA 

Tel: +54 11 4805 7287 

Fax: +54 11 4805 7287 

Email: sudamerica@allu.net 

5


Ramboll Finland Ltd. (previously SCC Viatek Ltd.) is part of the Ramboll Group, a leading Nordic 

consulting group with more than 4 200 employees in over 70 offi ces. The Ramboll Group operates 

in environment, construction, infrastructure and traffi c. Ramboll Finland Oy operates currently 

in 14 regions in Finland, and employs over 600 people. 

The Ramboll Finland units in Helsinki, Espoo and Luopioinen offer specialist services on mass 

stabilisation project dimensioning, planning and coordination as well as in quality control work. 

The company has completed hundreds of stabilisation projects, ranging from cases such as 

single-family houses to the expansion of major harbours, and has participated in most of the 

signifi cant stabilisation research and development projects in Finland since the 1980’s. Additionally, 

Ramboll Finland in Espoo and other locations offers fi eld services in soil investigation, 

production services and quality control work from start to a fi nal product. 

Picture: Mass stabilisation in a residencial area. 

R&D laboratory of Ramboll Finland in Luopioinen has been operating in the development of 

technologies and materials for environmental and geotechnical applications since 1989. It has 

completed over 250 R&D projects in column, mass, and layer stabilisation in Finland and internationally. 

In addition to stabilisation laboratory services, the R&D unit offers services in geotechnical 

and environmental testing, in-situ testing and quality control work, ground penetrating radar 

investigations, and instrumentation of fi eld test sites. 

6 



Mass stabilisation has traditionally been accomplished using cement and lime admixtures, but 

mass stabilisation using industrial by-products as stabilisers is becoming more common and 

gaining widespread acceptance. Industrial by-products including fl y ashes, blast furnace slag or 

calcium sulphate products are used to replace more expensive commercial binders, and these 

solutions are often less expensive and perform better than traditional methods. Approximately 

200 industrial by-products have been investigated by Ramboll in Luopioinen, and it is currently 

the leading laboratory in the Nordic countries for promoting by-products as potential binders. 

Picture: Vuosaari harbour, Helsinkin Finland 

A brief list of Ramboll Finland’s stabilisation projects includes : 

• Mass stabilisation of clay and peat in Limerick, Edenderry and Mossfi eld, 

Ireland (2005-) 

• Mass stabilisation in Valencia harbour, Spain; stabilisation tests and quality 

control (2004-) 

• Mass stabilisation of approximately 500 000 m 3 of dredged sediments contaminated by 

TBT (tributyl tin) in Vuosaari Harbour, Helsinki, Finland; services included 

construction planning, binder selection and optimisation (2003) 


7


• Stabilisation and utilisation of surplus materials (low quality soils) in Vuosaari 

harbour, Helsinki (2003-2004) 

• Combined mass and column stabilisation of the yards of IKEA in Vantaa, Finland 

(extremely diffi cult subsoil conditions); services included dimensioning, construction 

assistance and quality control work (2002-2003) 

• Laboratory services for stabilisation of dredged sediments in Trondheim Harbour, 

Norway (2002) 

• Mass stabilisation and combined mass and column stabilisation of peat and muddy 

clay in Kivikko and Haaga, Helsinki, Finland (parking lots and industrial area); 

several test fi elds and stabilisation projects; services included dimensioning, instru 

mentation, quality control and follow-up studies (1998-) 

• EuroSoilStab – European R&D project on soft soil stabilisation; leading project 

partner in Finland, binder development and testing, planning, dimensioning 

and follow-up studies of test stabilisations (1997-2000) 

For more information: www.ramboll.fi 

RAMBOLL FINLAND OY 

Piispanmäentie 5 

02240 ESPOO Finland 

Tel. + 358 20 755 611 

Fax + 358 20 755 6206 

Manager Mikko Leppänen (mikko.leppanen@ramboll.fi ) 

Manager Juha Forsman (juha.forsman@ramboll.fi ) 

RAMBOLL FINLAND OY 

Vohlisaarentie 2B 

36760 LUOPIOINEN Finland 

Tel. + 358 20 755 6740 

Fax + 358 20 755 6741 

Manager Pentti Lahtinen (pentti.lahtinen@ramboll.fi ) 

Project manager Harri Jyrävä (harri.jyrava@ramboll.fi ) 

8 



2. MASS STABILISATION 

2.1 What is mass stabilisation? 

Mass stabilisation is a relatively new ground improvement method for soft soil layers. Stabilisation 

is done by mixing an appropriate amount of dry or wet binder throughout the volume of the 

treated soil layer. The binder can consist of a single substance or be a mixture of various substances 

like cement, lime, fl y ash or furnace slag. New binders and binder mixtures using different 

industrial by-products are being introducted to the market continuously. Mass stabilisation 

may also be combined with another stabilisation method known as column stabilisation. 

The main purposes of soil stabilisation are: 

• To increase the strength of the soft soil 

• To improve the deformation properties of the soft soil (reduce settlements) 

• To increase dynamic stiffness of the soft soil 

• To remediate contaminated soil 

A B 

Figure. a) Mass stabilisation and b) combined mass and column stabilisation 

The mass stabilisation method has many benefi ts, including: 

• It is a rapid ground improvement method, and can be adapted to varying soil 

conditions 

• It is in most cases economically effi cient and saves materials and energy 

• It improves the engineering properties of the soil and can be fl exibly linked with 

other structures and with the surroundings (no harmful settlement differences) 

• Transfer of the natural soil elsewhere is not needed, so there is less transportation 

and traffi c pollution and no need for disposal sites and offsite transport. 


9


Environmentally, the mass stabilisation has only minor effects to the surroundings. Vibration and 

noise levels are low during stabilisation. Leaching and transport of harmful substances due to 

binder materials is insignifi cant, which has been confi rmed by extensive laboratory work in many 

stabilisation projects. 

The future of mass stabilisation methods looks quite encouraging. Results obtained from different 

projects clearly show that is possible to construct fi elds and embankments of a high quality 

at a moderate prize. Active research to develop both more effective binders and mixing tools has 

created new application areas, and has improved the competitiveness of mass stabilisation in 

comparison with traditional techniques 

2.2 Applications of mass stabilisation 

Mass stabilisation is especially suited as a ground improvement method for projects where economical 

reinforcement of wide areas are required. Natural applications of mass stabilisation include 

road, street and railway embankments, and yard and storage areas, where the thickness of the 

softest soil layers is at least a few meters (yards) thick and located at a maximum depth of 5 

meters (yards) below the ground surface. 

In areas where subsoil layers of higher load-bearing capacity are located a few meters (yards) 

from ground level, mass stabilisation may be used instead of soil replacement. In the case of 

thicker soft soil layers, mass stabilisation may in many cases replace the embankment piling under 

the road or street embankment. The mass-stabilised layer distributes the loads over a wider 

area, thereby limiting settlement. 

A relatively new application for mass stabilisation is solidifi cation of dredged mud, which has 

traditionally been considered unsuitable for any type of construction. Usually, dredged sediments 

are transported to disposal areas; however, problems are encountered when disposal areas are 

fi lled or when sediments are contaminated and thus unsuitable for standard disposal sites. Mass 

stabilisation can be utilised for both improving the properties of poor soil masses and binding the 

harmful particles into the stabilised soil. In a typical operation, the contaminated sediments are 

transported into a basin close to the dredging site, and transformed for example into a city park 

or a much-needed harbour shipping container fi eld. 

Mass stabilisation can be implemented also by mixing binders to soil that has been excavated 

and placed on the ground. Mass stabilisation improves the properties of the excavated, poor 

quality soil mass, so that instead of transporting this material to a landfi ll it may be used for other 

construction purposes such as road structures, fi ll, noise barriers, etc 

Mass stabilisation technology advances continually. As the stabilisation equipment and binder 

technology are developing, it is possible to adapt new modifi cations to mass stabilisation. 

10 



Pictures: Mass stabilisation in Trondheim harbour 

A few examples of projects in which mass stabilisation may be feasible are: 

• Road, street and railway construction sites 

• Yards, parking lots, sports fi elds, and storage construction sites 

• Foundations for industrial buildings and bridges, pools, and landfi ll areas 

• Noise barriers and slopes of rivers, lakes, roads, etc. 

• Traffi c vibration elimination 

• Solidifi cation/stabilisation of dredged sediments 

• Stabilisation of very soft soils for tunnel boring 

• Cable/pipe channel construction sites 

• Protection of adjacent structures 

• Reduction of earth pressure 

• Protection layers under the water 

• Ground water protection layers 

• Protection layers for permafrost and frost 

• Handling of waste and contaminated soil: solidifi cation, isolation and neutralisation 


11


2.3 Mass stabilisation versus other methods 

ew project the soil reinforcement method or combination of methods are compared and the most 

suitable one is chosen. Soil improvement using mass stabilisation compared with alternative 

methods, and their relative advantages and disadvantages, are listed below. 

12 

Mass stabilisation Other methods compared to 

mass stabilisation 

Figure: Mass stabilisation compared with other methods 

There can be avoid the building walls to pipe trench by stabilising 

the pipe trench before diging ditch. 



Figure: Mass stabilisation process as an alternative for mass exchange in the Vuosaari 

Seaport project (Helsinki, Finland) 

Amount Mass 

excange 

Stabilisation 

commercial 

binders A 

Stabilisation 

by-product 

binders B 

The total cost of project is one of the principal factors when choosing the soil reinforcement 

method. Following example gives an idea how different alternatives can be roughly compared to 

each other. 


Save Save 

A B 

m3 € € € € € 

150.000 4.240.000 2.400.000 1.740.000 1.840.000 2.500.000 

Cost savings through mass utilisation within the Vuosaari Seaport project (Helsinki, Finland) 

13


Example 

New road (length 100, width 10 m) is planned to build on a very soft clay/mud. Alternative reinforcement 

methods for this road are mass exchange, piling and mass stabilisation. The costs of 

the methods are compared here. 

A. Mass exchange 

14 

5 m 

3 m 

5 m 

3 m 

5 m 

3 m 

2:1 

12 m 

New road 

Mass exchange 

10 m 

New road 

Piles 

10 m 

New road 

Mass stabilisation 

Soft 

clay/mud 

Silt 

Moraine/till 

Soft 

clay/mud 

Silt 

Moraine/till 

Soft 

clay/mud 

Silt 

Moraine/till 


• Volume of material to be excavated 

= 47 m3 ≈ 50 m3 

• Cost of the surplus material ≈ 15€/m 3 

• Cost per 1 m of road = 750 €/m 

=> 75 000 € / 100 m 

B. Piling and slab 

• Concrete piles, diam. 250 mm, 

c/c = 2,0 m 

• Cost of one pile 

20 €/m x 8 m = 160 € 

• Cost of piles 

(160 x 6)€ / 2 m = 480 €/m 

• Slab h=250 mm, 40 €/m2 

• Cost of slab 

40 €/m2 x 10 m =400 €/m 

• Cost per 1 m of road =880 €/m 

=> 88 000 € / 100 m 

C. Mass stabilisation 

• Volume of material to be stabilised 

= 50 m3 

• Cost of the stabilisation ≈ 12 €/m3 

• Cost per 1 m of road= 600 €/m 

=> 60 000 € / 100 m

ALLU STABILISATION SYSTEM 

3. ALLU STABILISATION SYSTEM 

3.1 ALLU stabilisation machinery 

ALLU Stabilisation System is developed for mass stabilisation of soft soils, but it can also be 

used in the treatment of contaminated soils, by encapsulating contaminants within the soil and 

preventing them to leach to the surrounding areas. Stabilisation is successful only when using 

equipment and techniques that can homogenise the soil mass effectively and accurately. Additionally, 

the feeding accuracy is essential, along with quality control and reporting. 

ALLU Stabilisation System consists of three elements: 

• ALLU PM Power Mix (PM) 

• ALLU PF Pressure Feeder (PF) 

• ALLU DAC. Data Acquisition Control (DAC.) 

ALLU Stabilisation System uses dry binder and dried compressed air to transport the binder from 

the container into the soil. The binder is fed through the hose directly into the middle of the mixing 

drums of the PM. With the DAC. the operator can control all the functions of the PF and can 

also accurately set the amount of the binder to be fed into the soil. With these elements the mass 

stabilisation can be completed successfully and economically. 

The ALLU Stabilisation System is now patented throughout the world. 

More information on ALLU Stabilisation System machinery is found on the ALLU web site 

(www.ALLU.net). 

3.2 Technical information of the ALLU PM 

ALLU PM Power Mix is a versatile hydraulic operated mixing unit for excavators. When the Power 

Mix is attached to an excavator, the combination converts to an easily movable and effective 

mixing plant. 

ALLU PM Power Mix is able to handle very diffi cult and different kinds of materials effectively, 

such as clays, peat, sludge, mud and contaminated soil. The mixing effectiveness is based on the 

intelligent horizontal positioning of the drums and unique construction of the mixing elements. 

The drums move and mix material in all three dimensions simultaneously. The horizontal drums 

can transfer soil during the treatment and it enables to process materials in thinly layered sections 

to the desired depth. 

The reaching limit for Power Mix depends on the reach of the excavator and the size of the PM. 

At the moment the depth of mass stabilisation is up to 5 meters. 


15


TYPE WEIGHT (kg) BASIC MACHINE 

(EXCAVATOR) 

16 


MAXIMUM WORKING 

DEPTH (m) 

PM 200 1900 kg (+adapter 200 kg) 20 - 30 t 2 m 



Picture: ALLU PM


3.3 Technical information of the ALLU PF and ALLU DAC. 

The ALLU PF Pressure Feeder feeds dry binder from the container, through the hose, and directly 

into the middle of the mixing drums of the PM. The unit is mounted on a tracked chassis and is 

remote controlled, allowing the unit to follow behind the excavator onto the site. 

Two PF models are available: PF 7 with one 7 m³ container and PF 7+7 with two 7 m³ containers, 

which are pressurised with a compressor. The maximum pressure is 8 bars and air productivity 

5 m³/min. Feeding capacity is up to 5 kg/sec and the amount of the binder can be set and adjusted 

accurately (accuracy 0,1 kg/s), also during the working with the DAC. system. 

ALLU DAC. Data Acquisition Control system measures, controls and reports the feeding operation. 

ALLU DAC. enables control of the entire Stabilisation System, making the system user-friendly, 

and provides the facility to transfer data onto other computers. Thus the work done is properly 

documented for quality control purposes. 

Pictures: ALLU PF 7+7 with dust fi lter system and ALLU DAC. 


17


3.4 Principles of ALLU mass stabilisation 

There are three different working principles for the ALLU Stabilisation Systems. 

Stabilisation in different layers 

The method is used when material is solid enough. The binder material is either spread on the 

surface or fed directly to the mixing drum while the drum is rotating. While mixing the binder and 

soil the PM is also moving the stabilised material towards the excavator. The depth of stabilisation 

is not limited by the length of the PM. 

Figure: Stabilisation in layers 

Stabilisation in blocks 

The method is used when the material is very wet (peat, mud or soft clay). The binder is always 

fed into the middle of the mixing drums while the drums are rotating and simultaneously moved 

vertically. 

The depth of the stabilisation is limited 

by the length of the PM (2,0 ; 3,0 or 5,0 

meters). The total area is usually divided 

into 10 to 25 meters square areas 

which are marked on the ground with 

the sticks and the stabilisation is done 

in one sequence. The driver moves the 

PM up and down to the required depth 

in every area so that the whole volume 

is homogenised. The amount of the 

binder is also controlled, adjusted and 

reported by using the DAC system. 

18 

Picture: Stabilisation in blocks 


Blocks


Stabilisation in recycling area 

Stabilisation in container or in pile could be a combination of methods mentioned earlier. 

Figure: Stabilisation in recycling area 

3.5 Cost Savings with the ALLU Stabilisation system 

The ALLU system represents an advance in terms of cost savings during mass stabilisation projects. 

Most of the expenses in a stabilisation project come from the binder, which represents 

about 50-70 % of the total project cost. Here is one example of how accuracy of binder feeding 

affects to a cost of a project. 

Case 

The amount of the soil planned to be stabilised is 50 000 m 3 and the optimised binder 

quantity is 120 kg/m 3 

• Binder quantity is 120 kg/m 3 x 50 000 kg = 6 000 t 

• The cost of the binder is 70 - 120 € / t 

• The total cost of the binder ranges from 420 000 € to 720 000 € 

• If the feeding of the binder is not accurate, 10 % excess binder could potentially be used. 

In this case additional project costs could be 42 000 € - 72 000 € 

This example case clearly illustrates that accurate measurement of binder quantity is es 

sential to the cost-effectiveness of a mass stabilisation project. Therefore, one of the main focus 

points in the design and development of the ALLU stabilisation system was accurate measurement 

of binder feeding rates. 


ALLU PF 

19

MASS STABILISATION IN A NUTSHELL 

4. MASS STABILISATION PROJECT IN A NUTSHELL 

Every stabilisation project is unique and different soil conditions and functional requirements, 

but a typical mass stabilisation project consist of sections listed below. 

A. SITE AND REQUIREMENTS 

- The subsoil conditions are unsuitable for construction, need for subsoil 

reinforcement 

- Shear strenght / bearing capacity needed 

→ Comparision of different reinforcement methods, basic designing 

→ Choosing the mass stabilisation method (alone or combined with other methods) 

- Environmental requirements 

B. COLLECTION OF INFORMATION 

- Existing information on soil conditions and structures located in the site 

- Possible pollution of the site 

- Field surveys 

- Pretests 

C. LABORATORY WORK 

- Selection of binder quantity and quality by stabilisation tests 

- Properties of untreated and stabilised soil for the designing 

- Optimisation of binders 

D. DESIGNING 

- Calculation and designing of mass stabilisation 

- Requirements documents and for construction 

E. CONSTRUCTION 

- In-situ stabilisation tests 

- Execution of work 

- Documentation 

F. QUALITY CONTROL 

- Quality control before, during and after construction 

20 


FIELD SURVEYING 

5. FIELD SURVEYING 

5.1 Field tests and investigations 

Prior to the mass stabilisation project, fi eld investigations and laboratory tests are performed 

to determine the characteristics of the soil layers, the requirements for the binders, the area of 

the mass stabilisation and the lay-out of the design. In general, the site investigation will take 

place before the design process of the project is started. Because of the local subsoil is used 

as a constructive part of the mass stabilisation method, mass stabilisation requires a detailed 

site investigation. It is important to know the characteristics of the subsoil, to be able to make a 

proper decision on the exact location of the project, and to make a plan of good quality. 

Field investigations should be completed as early as possible, because then a volume of stabilisation 

(m3) can be calculated, and a cost estimate and time schedule can be developed. 

Also the most economical method of stabilisation (mass stabilisation, combined stabilisation) 

can be chosen and technical diffi culties of the project can be predicted and resolved before the 

stabilisation work. If further investigations are required, they can be completed well before the 

stabilisation work starts 

The main purpose of the site investigation is the identifi cation and description of the characteristic 

soil layers. A secondary objective is to identify the presence of obstacles in the subsoil. If 

necessary, the site investigation can be done in two phases. 

The preliminary investigation provides details regarding geological contacts and soil types prevalent 

at the site, and can be used to develop a preliminary design and cost estimate. Additionally, 

technical challenges can be identifi ed. The investigation can be completed using CPT-tests and 

geotechnical borings to obtain suffi cient information for preliminary design purposes. Ground 

penetrating radar (GPR) investigation is suitable for peat layer surveys. Also in this stage samples 

for the laboratory are collected. 

In the second phase, the 

fi nal design is developed 

based on a detailed site 

investigation, which is 

required to complete a 

high-quality design for 

mass stabilisation. 

Picture: Sounding with 

middle-heavy drilling 

machine with static-dynamic 

penetration test 

and drilling equipment. 


21

FIELD SURVEYING 

5.2 Investigation methods 

A variety of in-situ testing methods have been employed to obtain information for stabilisation 

projects in different countries. The table below lists some of the available methods used, but 

also other investigation techniques do exist. Selection of exploration method(s) depends on the 

size of site, its soil conditions, and on the planned use of the site after of the stabilisation. When 

fi brous peat is present, special attention must be paid to the reliability of the test results. 

Method Information 

Collection of existing information - Existing information on soil conditions 

Possible contamination 

Existing structures on the site (pipe lines, old 

dumping places, ect.) 

CPT (cone penetration testing) or other type of 

soundingCPTu (CPT with pore pressure measurement) 

22 

- Thickness of layers 

Relative range/variation of strength 

Hydrological situation 

Vane shear testing - In-situ undrained shear strength of clay layers 

Test pit - Thickness and soil type of layers 

Disturbed samples for the laboratory 

Georadar investigation - Thickness of peat layers 

Disturbed samples - Properties of soils (soil type, water content, density, 

grain size distribution, clay content, pH, organic 

content, sulphides) 

Samples for stabilisation tests in laboratory 

Undisturbed samples - Compression properties of clay layers 

Consolidation degree and bulk density 

Samples for stabilisation tests in laboratory 

Standpipe Piezometer - Ground water level 

Rising head test in a standpipe or other in-situ - Permeability estimate (in-situ) 

permeability test 

5.3 Samples for the laboratory 

Stabilisation testing and optimisation of the binder quality/quantity can take up to 6 months, if 

done properly, and therefore it is recommented to collect samples as soon as possible in a beginning 

of a project. 

Samples are collected in the fi eld by means of a special sampler or from a test pit. Samples should 

be taken vertically down to the planned stabilisation depth, which generally is a harder bearing 

layer beneath softer soil layers. The number of samples depends on the size of the planned stabilisation 

and variation of the soil conditions. Samples should be representative of the site to the 

extent possible, so that suitable binder type and quantity (kg/m3) may be selected. 

The number of soil samples needed for laboratory testing is determined after collecting the basic 

information about the site and its intended future. Sealed samples with information of sampling 

place, depth and date should be stored in cool place before sending to the laboratory. Undisturbed 

samples must be handled with care. 


LABORATORY WORK 

6. LABORATORY WORK 

6.1 Determination of soil properties 

Geotechnical properties of stabilised soil are dependent on the physical and chemical properties 

of the natural soil reserves and on the properties of the binder. The most important geotechnical 

properties of organic soils that have effect on the stabilisation are grain size distribution, natural 

water content, organic content and decomposition degree, and pH. 

The laboratory testing program can be divided into the following: tests for soil classifi cation and 

chemical properties, tests for engineering properties, and tests for environmental properties. 

Tests excluding environmental tests are described in detail in Euro Code 7, Part 2 “Design assisted 

by laboratory testing”, which covers requirements for the execution, interpretation and use 

of results of laboratory tests to assist in the geotechnical design of structures. 

Classifi cation and chemical properties 

Tests are performed to obtain information on subsoil and to support the choice of the type and 

amount of binder. The tests should be performed for each individual soil layer. The following parameters 

may be determined: 

• Water content and density 

• Grain size distribution and fi nes content 

• Organic content 

• Decomposition degree for peat (Von Post) 

• Liquid limit (LL), plastic limit (PL), plasticity index (PI) and sensitivity 

• pH 

• Sulphate, chloride and carbonate content 

• Humic acids/TOC and cation exchange capacity 

• Electric conductivity 

• Groundwater pH 

Engineering properties 

For the determination of a representative set of engineering properties, tests should be performed 

for each individual soil layer. Engineering properties are important mainly for the stabilised soil 

samples, but in some cases they are measured for the original soil as well, for the purposes of 

comparison and to facilitate design. This gives the designer an estimate of the improvement of 

the soil. Following parameters may be determined: 

• Unconfi ned compressive strength after 7, 28, 90, or more days after mixing 

• Development of strength over time 

• Compressibility 

• Permeability (capacity to allow fl uid to infi ltrate or to fl ow through the stabilized soil) 


23


The shear strength properties are determined using, for example, unconfi ned compression tests, 

triaxial tests, or the fall-cone test. In the absence of laboratory testing, another method for estimating 

the engineering characteristics of the in-situ soil is to use CPT sounding results. A good 

estimation is that the undrained shear strength is 5 - 10% (depending on the type of soil) of the 

cone resistance of a particular soil layer. In case of soils with high organic content this method 

is recommended. 

Environmental properties 

To determine the environmental impact of the stabilisation, tests should be performed. The relevant 

environmental properties are: 

• Available concentration of ion and metals from leaching tests 

• Type and total concentration of ions and metals. These tests are used as a 

refer ence measurement for leaching tests. 

• pH 

• Cation exchange capacity 

• Sulphide and carbonate content 

6.2 Properties of the stabilised soft soils 

As a result of stabilisation, the chemical and physical properties of clay, gyttja and peat will 

change signifi cantly. The pH-value of the stabilised soil will quickly increase to 11-12, and the 

curing process starts. Depending on the type and quantity of binder some of the chemical reactions 

will proceed rather quickly (during the fi rst days) but some of the reactions may develop 

more slowly; total reaction time may be months or even years. 

The strength of the stabilised soil depends on the properties of the natural soil, type and quantity 

of binder, curing time, and homogeneity of the mixing work. The undrained shear strength of 

stabilised soil is normally within the range of 50 to 150 kPa. Samples of stabilised soil prepared 

in a laboratory may have undrained shear strength of several hundreds of kPa, but such high 

values are rarely obtained in-situ due to natural variation in soil conditions and in accurance in 

mixing work. 

The relation between the curing time and the strength of the stabilised soil is important, because 

it governs the acceptable rate of loading. This relation depends on the soil type and the quality 

and quantity of binder. Additionally, the temperature during curing time can affect to the speed 

of curing, but usually the impact is relatively small. If only cement is used as a binder, most of the 

strength develops during the fi rst month after stabilisation. When using binders including lime, 

gypsum, furnace slag and/or ash the strength will still continue increasing after the fi rst month. 

The geo-mechanical properties of the stabilised material largely depend on the type of binder. In 

general, strength and brittleness of the stabilised soil increases with increasing cement content. 

In contrast, ductility increases with increasing amount of lime. 

24 



6.3 Stabilisation testing 

To ensure the quality of the fi nal stabilised product, a number of stabilisation tests must be 

performed in the laboratory beforehand to determine the most suitable binder, to optimise the 

binder quantity, and to determine the engineering characteristics of the stabilised soil for the 

actual case. Prediction of the properties of stabilized soil can be made after classifi cation tests 

and preliminary estimation of stabilisation properties, binder type and quantity. 

Stabilisation testing and optimisation of the binder quality/quantity can take up to 6 months, if 

done properly. Testing can be done in a shorter time, but then the number of test specimens and 

performed tests increses, because there is no time for result evaluation and further optimisation 

during stabilisation testing. Also the long term curing effects of different binders cannot be taken 

in consideration, if tests are discontinued after only one month. 

In principle the stabilisation testing is done according to the fl ow chart presented in this chapter. 

Parameters determined by laboratory tests are described in Chapter 6.1. 


25


Figure. Laboratory procedure in a stabilisation testing 

26 

2nd 

optimisation 

1st 

optimisation 

Unconfi ned 

compression 

strength 

Homogenisation of soil samples 

Classifi cation and chemical properties 

- water, content, grain size distribution, clay 

content, density, pH, von Post etc. 

Selection of binder / binder mixtures and 

their quantities for testing, based on 

- knowledge gained on previous projects 

- available binders 

Unconfi ned compression 

strength after 7/14 days 

Optimisation of binder quantity 

(additional test specimens and their testing) 

Mixing of soil and binders and 

making of test specimens 

Storing for 

0, 7, 14, 28, 90, ...days 

Compressibility Permeability Environmental 

testing 

Interpretation of test results 

Choosing the suitable binder and its 

quantity 



In some cases the frost susceptibility (resistance to frost) and freeze-thaw durability (resistance 

to freezing and thawing cycles) should be determined. Permeability of the stabilised mass should 

be measured in laboratory, in case mass stabilisation is being used for solidifi cation of contaminated 

soils. 

In the environmental laboratory the binder content of stabilised sample is determined by x-ray fl uorescence 

measurements. Additionally, the amount of total hydrocarbons and leaching of harmful 

particuls can be tested, but these test are performed only when the subsoil is contaminated 

or when an untested industrial by-product is used as a binder component. 

In Ramboll, choosing binders or binder mixtures for testing is based on extensive knowledge 

from over 250 R&D projects since 1989 on deep, mass and layer stabilisation. Ramboll has 

specialised in utilisation of industrial by-products and about 200 by-product materials have been 

investigated and tested for the different applications. 

Pictures: Making, loading and testing of a stabilised peat specimen 

About 50-70 % of the total costs in stabilisation project is caused by the binder. By careful laboratory 

work the suitable binder and its optimised quantity [in kg/m3] is selected and thus considerable 

savings are reached. 

Example 

• The amount of the soil planned to be stabilised is 100 000 m3. 

• Binder A, required quantity 120 kg/m3, price 100 €/t 

=> (0,12 x 100 000 x 100) € = 1 200 000 € 

• Binder B, required quantity 150 kg/m3, price 70 €/t 

=> (0,15 x 100 000 x 70) € = 1 050 000 € 


27

BINDERS 

7. BINDERS 

7.1 Binder types 

Binders may be hydraulic or non-hydraulic. A hydraulic binder is self curing in contact with water, 

while a non-hydraulic binder requires a catalyst to initate curing. Non-hydraulic binders may 

be used to activate latent hydraulic materials to produce reactive blended products. A hydraulic 

binder will stabilise almost any soil but the mechanical mixing of the binder into the soil must be 

very precise, otherwise the result will be heterogeneous. Non-hydraulic binders generally react 

with clay minerals in the soil, which will result in stabilised material with improved geotechnical 

properties. 

New binders, produced as by-products of industrial processes, can be used for mass and deep 

stabilisation. In some cases, they can be even more suitable for stabilising organic soil and peat 

materials than traditional binders. Binders available as by-products, or by-product based mixtures, 

are much cheaper on a mass basis than traditional lime-cement binders. About 50-70 % 

of the cost of a mass stabilisation is caused by a cost of a binder, and therefore cheaper binder 

means savings for the mass stabilisation project. 

Cement 

Cement is a hydraulic binder and is not dependent on a reaction with minerals; generally, it may 

be used to stabilize almost all soil material. There are various types of cement, and in general 

ordinary Portland cement is used for stabilisation purposes. Cement with fi ner grain size is more 

reactive. Different additives such as slag, ash or gypsum may be added to other types. Care must 

be taken to ensure homogeneous mixing, because cement, unlike lime, does not diffuse into the 

surrounding soil mass. 

Lime 

For stabilisation purposes, lime is used in two forms: quick lime (CaO) and hydrated lime (Ca(OH) 2 ). 

Lime stabilisation is based on a reaction with minerals in soil or with added mineral materials. 

Quick lime reacts with the water in the soil and forms hydrated lime. In addition to chemical 

binding of water, this reaction also releases heat which will contribute to faster reactions and a 

reduction of water content. During the reaction, ion exchange reactions occur which affect the 

stabilised soil structure. Long term stabilisation reactions, like pozzolanic reactions, may continue 

for years after completion of stabilisation work. 

Blast furnace slag 

Slag needs to be granulated and ground to be reactive; fi ner grain size produces more reactive 

slag. Slag is activated with lime or cement to achieve a faster reaction. Chemically, slag is similar 

in composition to cement but its quality and reactivity varies. Blast furnace slag may be regarded 

as a low cost substitute for cement and is normally used as part of a blended product. The long 

term curing effect (strenght development) of slag continues even years after stabilisation and in 

many cases cement-slag mixture is more effi cient than cement alone, if results are compared 

later on. 

28 


BINDERS 

Ash and FGD 

Ash is a fi ne grained residue from a combustion process. Composition of ash varies depending 

on the fuel and the burning process. Most common fuels are coal, peat and bio fuels. Fly ash is 

collected from fl ue gases with fi lters. 

FGD is the end product of fl ue gas desulphurisation and its composition varies from pure gypsum 

to almost inert calcium sulphate. Limestone or lime is often used as a sorbent to capture sulphur 

from the fl ue gases. 

Pozzolanic reactivity of ash varies within wide ranges, and therefore should be determined for 

each product separately. Ashes are as a rule not very reactive by themselves, but may reduce the 

cost of a blended product. If fl y ash is mixed with FGD it may have reduced reactivity. 

Calcium sulphate products 

Calcium sulphate may be derived from a number of industrial processes as a secondary product. 

Solubility of gypsum produces Ca- and 

SO4-ions, which activate for example 

blast furnace slag and fl y ash. In combination 

with soluble aluminates gypsum 

reacts to form ettringite. Calcium 

sulphate products are used as components 

in blends. 

Blends of dry binders 

The above-mentioned materials may 

be blended with each other in different 

proportions to optimise technical performance 

and economy with respect to 

the soil that will be treated. Blends may 

be factory-produced or mixed at site by 

the stabilisation equipment. Picture. Materials from laboratory testing: dredged sediment, 

cement and fl y ash; gypsum, stabilised specimen 

and fi bre clay (paper industry by-product) 

7.2 Binders for different soil types 

The geotechnical and chemical properties of the soil and the choice for the appropriate binder 

have a signifi cant affect on the results of stabilisation. Typical binder quantity values vary from 

100 kg/m3 up to 250 kg/m3. 

The most important binder components are cement, lime, blast furnace slag and gypsum. Additionally, 

fl y ash is commonly utilized, most notably for the stabilisation of peat. Binder mixes 

consisting of 2-components are widely used, but 3-component binders are more versatile and 

can be more effective for many cases. 


29

BINDERS 

Typical organic 

content 

30 

Silt Clay Organic Soils 

Gyttja/Mud, 

Organic Clay 

Peat 

0-2 % 0-2 % 2-30 % 50-100 % 

Binder 

Cement xx x / x(x) x / x(x) xx / xxx 

Cement+gypsum x x xx xx 

Cement+furnace slag xx / xx(x) xx / xx(x) xx xx / xxx 

Lime+Cement xx xx x - 

Lime+gypsum xx xx xx - 

Lime+slag x x x - 

Lime+gypsum+slag xx xx xx - 

Lime+gypsum+cement xx xx xx / xx(x) - 

Lime - Lime - - 

xxx very good binder in many cases 

xx good binder in many cases 

x good binder in some cases 

- not suitable 

Table. Approximation of suitability of binders or binder mixtures on a stabilisation of Nordic soils. 

Based on relative strength increases after 28 days in a laboratory. (EuroSoilStab 2002) 

7.3 Added sand in mass stabilisation 

In some projects sand is added in order to ease the stabilisation work and it is believed to guarantee 

more homogeneous result. Sand should be clean and frost-resistant. A typical addition 

rate for sand is 100-150 kg/m3, which is used in soft peat stabilisation. Sand is spread on top of 

the cleared and stripped ground before the stabilisation, and is mixed in during the process. 

7.4 Effects of binder quantity, curing time and preloading 

The effect of binder quantity on the strength of the stabilised soil has been tested in the Ramboll 

laboratory and the results are shown in the following fi gure. It should be noted that the quantity 

vs strength curves are not linear; that is, some binders have a threshold value point in wich the 

strength starts to grow more rapidly. In other cases, some binders are almost insensitive for the 

quantity (quantity affects only a little for the strength). 

The effect of curing time differs between different mixes of binder and soil. When using only cement 

as binder the stabilisation reactions will almost totally be fi nished during the fi rst month. In 

contrast, the stabilisation process of materials containing lime, furnace slag, gypsum or fl y ash 

can continue for several months after mixing. As a result, laboratory tests should be extended for 


BINDERS 

some time, to optimize the binder mixture: the results may show greater applicability for a slow 

curing binder that produces higher long term effects, but these results may not be observed if 

tests are discontinued after only one month. 

Preloading of a mass stabilised area will signifi cantly affect the stabilisation of peat. Therefore, 

the importance of preload embankment should be considered, and the scheme of preloading 

should be planned accordingly. The possible preloading scheme will be determined by the stability 

of the embankment. The use of embankment will be taken into consideration while planning 

Unconfined compressive 

strength [KPa] 

600 

500 

400 

300 

200 

100 

0 

Unconfined compressive strength after curing of 28 days 

Dredged sediments, w = 64-100% 

0 50 100 150 

Binder quantity [kg/m3] 

Cement+lime 


Cement 

Cement+slag 

(sediment type I) 

Cement+slag 

(sediment type II) 

Figure. Example on the effect of binder quantity on unconfi ned compressive strength 28 days 

after mixing 

Material: Clay 

w = 134,5 % 

Loi = 9,5 % 

pH = 7,9 

Curing time and compression strength, 60 

kPa 

400 

350 

300 

250 

200 

150 

100 

50 

0 

kg/m 3 

28 d 90 d 180 d 

Cement 197 232 261 

Cement+slag 1:1 103 161 350 

Cement+CaO 1:1 142 183 268 

FTC 79 116 123 

FTM 39 67 87 

Figure. Example on the curing time effect and compression strength of different binder mixtures. 

FTC and FTM are lime/gypsum based commercial binder materials. 

31

BINDERS 

7.5 Effect on permeability 

Stabilisation affects the permeability of the 

soil signifi cantly. Binders based on lime or 

lime-cement mixes might increase considerably 

the permeability of clay. In contrast, 

gypsum and cement binders generally decrease 

the permeability. While binder addition 

causes a change in permeability, the 

change is relatively insenstive to time. For 

example, permeability tests on peat with different 

binders indicate that the permeability 

(k) of stabilised peat is between 10 -9 … 10 -8 

m/s as well after 28 days as after 180 days. 

7.6 Environmental acceptability 

32 

Picture: 3-axial permeability test 

Environmental tests are usually required by environmental authorities and performed before 

a stabilisation in a contaminated soil area. Testing is done to assur that harmful particles will 

not migrate from the stabilised area to the surroundings. Sometimes environmental testing is 

required when using industrial by-products as binders or binders components. 

Leaching tests are chosen to determine the leaching behaviour and potential environmental 

harm of the stabilised soil when using different types of binders. Normally, leaching of stabilised 

clay and gyttja is tested by the diffusion test (NEN 7345, NEN 7347 or similar). The column test 

(NEN 7343, CEN/TS 14405 or similar) is suitable to test leaching of stabilised peat. 

Picture: Leaching tested with column test 


In the EuroSoilStab-project (1997) the 

leaching tests were made on different stabilised 

soils and for comparison on natural 

soils as well. The stabilised soils were chosen 

to contain binders based on industrial 

by-products like fl y ashes, furnace slag and 

gypsum. The results indicate that there is no 

increased risk to the environment by using 

binders, based on lime and cement as well 

as the tested industrial by-products.

DESIGNING 

8. DESIGNING 

Note! This chapter contains only an outline of a mass stabilisation designing and with this information 

no actual designing can be implemented. 

8.1 Design requirements 

The design is developed for the most critical section of the design, which is the most unfavorable 

combination of load effect and bearing capacity likely to occur during construction and in service. 

For design purposes mass stabilised soil is assumed to be a homogeneous elasto-plastic soil 

layer. The uncertainties of the result of mixing and homogenisation of the stabilised soils must 

be considered in the design. 

The stabilisation program must be designed and executed such that during its intended life the 

supported structure will remain serviceable for its required use and serve its intended purpose, 

with reasonable reliability and economy. This requires that it satisfy ultimate and serviceability 

limit states. 

The requirements for the service life and ultimate and serviceability limit states must be specifi 

ed by the client based on the project needs. The design must be in accordance with the requirements 

of Euro Code 7 and/or with national regulations. In soil parameter values a distinction is 

made between measured, derived, characteristic and design values. 

The derived value is the value of a ground parameter obtained by theory, correlation or empiricism 

from the measure test results. A characteristic value is determined from the derived values 

to give a conservative estimate of the value affecting the occurrence of a limit state. 

Service life 

The stipulated service life is specifi ed in construction specifi cations. 

Limit states 

The design of stabilised ground must satisfy ultimate and serviceability limit states. 

To satisfy ultimate limit requirements, the design of the stabilised ground must be such that 

there is a low probability of collapse or other failure which would limit its function, a risk of danger 

to people, or signfi cant economic loss. Mass stabilisation is designed so that a structure or 

embankment and its close surroundings have satisfactory overall stability, and so that failure of 

the structure or its parts does not occur due to excessive deformation. 

To satisfy serviceability limit state requirements, a mass stabilised area, including transition 

zones to unstabilised embankments, must be designed so that the total and the differential 

settlements along and example across the road surface satisfy the requirements for serviceability. 

Additionally, long-term creep movement should be considerated. 


33

DESIGNING 

8.2 Loads 

The loads are specifi ed by the client. Calculation of stability during construction often yields the 

lowest factor of safety. Traffi c load during construction can be restricted by agreement with the 

client. The restrictions are set out in construction specifi cations. 

8.3 Characteristic material values 

Characteristic values are set out in construction specifi cations and are chosen as conservative 

selected values taking the design situation into consideration. 

Characteristic values of mass stabilisation properties may be based on fi eld tests, on fi eld trials, 

or on the results of laboratory tests made on specimens mixed in the laboratory. Char-acteristic 

values based on laboratory-mixed samples must consider the difference between laboratory and 

fi eld strength. 

The characteristic unit weight, Y k , (kN/m 3 ), of mass stabilised soil shall be based on results from 

laboratory tests made on specimens mixed in the laboratory. 

The characteristic undrained shear strength, c uk (kPa), is generally based on the results from 

fi eld tests on trial stabilisation or on unconfi ned compression test on specimens mixed in the 

laboratory. The difference in strength between laboratory mixed samples and fi eld tests should 

be considered carefully. 

The characteristic compression modulus, E k , in mass stabilisation is generally set equal to 

50-100 times c uk . Organic soils generally fall at approximately 50 times c uk and silty clays generally 

fall at approximately 100 times c uk . 

8.4 Design values 

The partial factors applied to the characteristic value for ultimate limit state depend on the particular 

design condition. The partial factors applied for the fi nal structure should be in accordance 

with local regulations, or determined on the basis of special investigation and specifi ed in 

the construction specifi cations. Lower partial factors, as recommended below, may be used for 

some temporary design situations. 

Unit weight of stabilised soil 

Design values of are equal to characteristic material values of Section 8.3. 

Strength and deformation properties of soil 

Parameters of unstabilised soil are determined by in-situ and/or laboratory tests. 

In calculating the ultimate limit state, the value of γm for strength parameters is taken from Euro 

Code 7 or national regulations. 

34 


DESIGNING 

In calculating the serviceability limit states, settlements are calculated with characteristic values 

in accordance with Euro Code 7 or national regulations. Total and differential settlements are 

then corrected with respect to the uncertainty of the calculated values (Euro Code 7 or national 

regulations). 

Design values shall be based primarily on fi eld tests. Design values based on laboratory mixed 

samples must consider the difference between laboratory and fi eld strength. 

Mixing trials are performed for characteristic soil strata. To provide a basis for the determination 

of the quantity of binder required in stabilisation, several mixes are normally tested in the laboratory. 

8.5 Design 

Calculation of settlements in the serviceability limit states 

Settlements within the mass stabilised area are calculated by assuming the mass stabilised 

volume behaves as a homogeneous, linearly elastic and perfectly plastic layer. All of the load q is 

carried by the mass stabilised volume. The strength must be chosen such that the yield strength 

of the stabilised soil is not exceeded. The settlement is calculated in accordance with Equation 

(a). Note that considerable settlements can be derived during the curing period (when the load 

only consists of the working platform) and these settlements must be calculated separately. 

S = 

ΣΔh 

⋅ 

m 

where 

q 

M 

m 

(a) 

Sm = settlement in the mass stabilised volume, m 

Δh = stratum thickness, m 

q = load on mass stabilisation, kPa 

Mm = compression modulus of mass stabilised soil, kPa 

When using mass stabilisation, a preloading embankment should be applied soon after the stabilisation 

work. The embankment compresses the stabilised volume and increases its strength. 

The amount of settlement varies depending on the soil to be stabilised. For peat and dredging 

mud, large settlement can occur due to the compression (compression could be up to 30-35 %). 

In the laboratory procedure suggested for preparation and storing of test samples for Mass Stabilisation 

Applications it is suggested that the compression of the test sample be measured in the 

laboratory. These recordings can be used for calculation of the immediate settlements. However, 

this settlement develops rapidly, and the settlements of the mass stabilised layer during service 

are usually small. 


35

DESIGNING 

Rate of settlement 

When the effective stress in the soil is less than the preconsolidation pressure, settlement develops 

rapidly. 

When the effective stress in the soil exceeds the preconsolidation pressure, the rate of consolidation 

settlement in the stabilised soil stratum is calculated in the same way as for vertically 

drained soil. Experience shows that the changes in the macrostructure of the stabilised soil may 

affect the permeability, but whether the permeability increases or decreases depends on the 

type of binder and stabilised soil. 

As stated earlier, it is essential to make a prediction of the magnitude and rate of settlement 

during the preloading time. The rate of settlement as above holds only for the stabilised volume. 

Calculation of the rate of settlement below the stabilised volume is performed in the normal way, 

bearing in mind that the permeability of mass stabilised soil is often higher than the permeability 

of untreated soil and it can work as drain leading water into the top of the stratum. 

The design and time of placement of the fi rst preloading stage are of outmost importance due to 

the fact that 70 to 90 % of the total settlements occur during fi rst 30 days. 

36 


STABILISATION WORK 

9. STABILISATION WORK 

9.1 Stabilisation tests 

Stabilisation tests are done in order to get necessary information for the project and to confi rm 

that used mixing time and binder quantity lead to satisfying stabilisation results i.e. strength 

values, homogeneity and settlements are according the plans. Types, numbers and execution 

procedures of tests are determined by customer or consulting company and they vary from case 

to case. 

Mixing work 

Mixing work is optimal when the mixing result will not improve by increasing mixing work time 

(m3/h). Optimal mixing time determination in mass stabilisation will reduce quality control costs. 

Additionally, reliability of the mass stabilisation will be ensured, and most importantly the total 

quality of the mass stabilisation will increase. 

Mixing time (sec/m3) depends on stabilisation machinery used in the project and on soil conditions, 

but can be for example 20-30 sec/m3. Ideachip has wide experience on different kind of 

mass stabilisation conditions and thus it has collected extensive data base which can be utilised 

in new projects. 

Mixing work quality i.e. homogeneous of mixing can be controlled by portable x-ray fl uorescence 

equipment (Niton, Innov-X, ect.) or other in-situ method. In-situ measurements are calibrated by 

calibration curves made in a laboratory beforehand (more information see Section 10.2). Measurements 

are often checked by titration in a laboratory. 

Binder quantity 

Optimisation of the binder quantity is done by stabilising different blocks (like 4 x 4 m2) using 

different binder quantities. After certain time (2-4 weeks) the shear strength of stabilised blocks 

are determined by soundings (CTP, vane shear testing) and if necessary, samples are collected 

for laboratory testing. 

Test areas/embankment 

When the stabilised area is large and/or there is need for new stabilisation solutions, separate 

test areas are used and monitored for a longer time. In the test area mixing methods and times, 

different binders and different binder quantities can be compared by soundings, sample collection 

and analysis, and settlement measurements. 

9.2 Mass stabilisation work 

Every project is unique and accomplished in different way, but in principle the work is done in 

following order: 

1. Clearing of wood etc. from the area 

2. Harrowing and removal of underground stones, stubs etc, which might disturb 

stabilisation machinery 

. 


37

STABILISATION WORK 

3. Marking of stabilisation fi elds and blocks 

4. Surface excavation to the desired level 

5. Spreading of sand on the ground (if additional sand is used) 

6. Mass stabilisation, test blocks/fi elds 

7. Production stabilisation 

8. Quality control during work 

9. Levelling of stabilised soil 

10. Spreading of geotextile and making of compact layer and/or preload embankment 

11. Quality control and follow-up of the stabilised area 

A pre-loading embankment (usually 0,5 - 1,0 m) is used on the mass stabilised area, because it 

ensures consolidation of the stabilisation area, provides a working platform for machinery, and 

the mass stabilised area can be levelled to the desired elevation as a whole. The embankment 

should be constructed as soon as possible, for example within 24 hours, to get the full benefi t of 

its presence 

PF7 working PF7+7 working 

9.3 Mass stabilisation log sheet 

Contractor should maintain a log sheet during stabilisation, and after work present data to the 

client, including: 

• identifi cation information of stabilised blocks 

• starting and ending time of stabilisation of each block 

• dimensions and locations of blocks 

• top and bottom elevation of stabilised blocks 

• binder quality, quantity and feeding pressures per each block 

• mixing work done per block 

• weather during stabilisation 

• differences in stabilisation compared to the quality requirements 

• realization of mass stabilisation (boundaries, elevations) 

ALLU DAC. Data Acquisition System saves all data during the stabilisation project and provides 

the ability to transfer data onto other computers. Saved data includes basic information on stabilisation 

project, numbers of stabilised blocks, binder fl ow (kg/s) and working pressure (bar), 

starting and ending time of binder feeding, and total amount of used binders (kg). 

38 


QUALITY CONTROL 

10. QUALITY CONTROL 

10.1 Control procedure 

Quality control work is performed in accordance with the following fl ow chart. 

FIELD SURVEYS AND 

LABORATORY TESTING 

-company’s quality system applied 

in the field and at the laboratory 

PRE TESTING 

- field trial tests 

- quality control procedure testing 

- working methodology 

CONSTRUCTION CONTROL 

- quality control during stabilisation 

- quality control after stabilisation 

QUALITY VERIFICATION 

- quality reports 

Figure: Quality control procedure 


39


10.2 Quality control before construction 

Some laboratory work is required for the in-situ quality control. Calcium quantity in stabilised 

soil samples is used in binder quantity measurements. For the x-ray fl uorescence equipment the 

calibration curves are determined and they show correlation between the calcium content of the 

soil and different binder quantities on soil samples prepared at the laboratory. Calibration curves 

should be checked by titration tests. In pre-testing, some compression strength tests may also be 

performed for reference purposes. 

Soil conditions often vary signifi cally in different spots and depths of stabilisation site and in 

many cases it is recommended to use more than one calibration curve in a quality control work 

during construction. Soil samples for the calibration curves should be collected from representative 

spots and at least one or two samples should extend underneath the planned stabilisation. 

Quality control work is also performed when a test fi eld or stabilisation tests are done before 

construction (see Section 9.2). 

Picture: Calsium content measurements with Niton XL-742S 

X-ray fl uorescence 

40 



Binder quantity [kg/m3] 

200 

180 

160 

140 

120 

100 

80 

60 

40 

20 

10.3 Quality control during construction 

During the stabilisation process the binder contents of the stabilised layers are measured by 

using x-ray fl uorescence analysis equipment and calibration curves (see Chapter 10.2). Titration 

tests are performed as an only method for binder content analysis or they are combined with xray 

fl uorescence analysis for result checking purposes. If the titration results differ greatly from 

x-ray fl uorescence analysis results then a new calibration curve should be determined. Homogeneity 

and depth of stabilisation is checked from the samples taken for the laboratory and with 

soundings. Quality control is done by the contractor or by an independent controller. 

10.4 Quality control after construction 

The shear strength of the mass stabilisation is examined in the fi eld by CPT or other sounding 

methods. Soil samples are taken from the strengthened structure and the samples are examined 

in the laboratory by triaxial test, penetrometer tests and by checking the binder content of the 

samples. And if required, the pore water pressure and ground water level are monitored. 

Example 

Calibration curve for Niton XL-742S 

X-ray fluorescence equipment 

Example 

Peat 1,5 m 

Clay 3,8 m 

0 

0 10000 20000 30000 40000 50000 

Ca concentration [ppm] 

Mass stabilisation for contaminated sediments was done by dredging mud into a basin surrounded 

by an edge embankment. The width of the basin was about 17 m, length about 80 m 

and depth 4-5 m. The quality control tests were made after one month. The bearing capacity of 

the mass stabilised mud was measured using soundings in 9 points (total 15 tests). Vane shear 

testing was used in 5 tests and deep stabilisation penetration test was carried out 10 times. 


Mud 3,5 m 

Figure: Calibration curve for binder quantity determination with Niton XL-742S 

41


Figure: Mass stabilisation of dredged mud 

Example 

Mass stabilisation was done on an area with extremely diffi cult subsoil conditions (peat, construction 

waste, wood piles, old landfi ll). Stabilisation volume was 65 000 m3 and depth 2-5 m. 

For the quality control purposes 95 soundings were done 2-4 weeks after construction. 

10.5 Settlement monitoring 

Settlement calculation can be done by calculation programs like Limeset (Swedish Geotechnical 

Institute) or FEM-program Plaxis. The behaviour of the stabilised fi elds can be observed by installing 

settlement plates, inclinometers and pietsometers to the structures. 

Acceptable level of settlement is determined by client and it depends on planned usage of stabilised 

area. 

Example 

Mass stabilisation (depth of 3 m) was done in an area with layers of peat (thickness 2-2.5 m), 

organic clay (0.5-2 m) and clay. A 2 m embankment was built on top of the area in the following 

year. The behaviour of the stabilised area was observed by installing settlement plates, inclinometers 

and piezometers to the structures. Settlements plates were primarily installed on top of the 

mass stabilized peat, but some plates were put to the middle and lower parts of mass stabilisation. 

During 3 years the total settlement was 500-650 mm and it has caused by the consolidation 

of the clay layers below the mass stabilisation. The measured settlement of peat was less than 

20 mm and of stabilised muddy clay, 110-130 mm. According to settlement measurements the 

settling of the mass stabilised layer was relatively uniform. 

42 



10.6 Environmental acceptability 

Risks to the environment can be caused by leaching of harmful components either from the 

soil or from the binder. If needed, environmental acceptability of stabilisation is determined by 

making leaching tests in a laboratory. The leaching tests predict possible quantities of leaching 

for 10…100 years and often give higher values than actually occurs in stabilised structures. The 

results are compared to values given by national environmental administrative authorities. 

The leaching test results gained in the EuroSoilStab project indicate that there is no increased 

risk to the environment by using binders, based on lime and cement as well as the tested industrial 

by-products. 

Vibration and noise levels are low during constraction. 


43

CASES 

KIVIKKO IN HELSINKI, FINLAND 

PARKING PLACE AND INDUSTRIAL AREA INTO THE SWAMP AREA 

Size: total of 4 ha mass stabilisation by end of the year 2003 

Problem: Combined mass and column stabilisation for the whole area was too expensive 

Solution: Cut down costs by using only mass stabilisation for the part of the area 

Binder: Cement 100 kg/m 3 

Other additives: sand 150 kg/m 3 

Machinery: ALLU PM300 

Soil conditions: 

Wooded swamp area 

Soft peat, w=400-1000 % 

Muddy clay, w=150 % 

Clay, w=35-80 %, su=4-14 kN/m 2 , 

normally consolidated 

44 


Stiff silt (thin layer between the clay layers) 

Clay, overconsolidated 

Silt, sand and moraine 

Ground water level +17.2 … +18.2 m

CASES 

Test mass stabilisation in summer 

2000 

In 1 ha test area 3 m of peat and muddy 

clay were mass stabilised. Mass stabilisation 

decreased the settlements remarkably 

and eliminated the stability problem. 

In 2001 the mass stabilisation was chosen 

as the ground treatment method for 

the Kivikko. 


Mass stabilisation in 2001-2003 

By the end of the year 2003 the total 

amount of mass stabilisation was 4 ha. 

As a stabilisation result there is now a 

strong and carrying layer used as a yard 

for industrial premises. 

Settlements 

The behaviour of the stabilised fi elds was observed by installing settlement measuring 

instruments to the structures. In three years the total settlement was 500-650 mm and it was 

caused mainly by upper normally consolidated clay below the mass stabilisation. The settling of 

the mass stabilised layer has been rather even. 

Quality control 

The binder contents of the stabilised layers was measured by using x-ray fl uorescence analyse 

equipment. The shear strength of the mass stabilised layer was examined in the fi eld by CPTsoundings. 

Soil samples were taken from the strengthened structure for the laboratory testing. 

45

CASES 

TRONDHEIM HARBOUR, NORWAY 

STABILISATION OF CONTAMINATED SEDIMENTS DURING 2002-2004 

Size: 11 000 m 3 of sediments 

Problem: Disposal of dredged sediments with low stability and containing PCB, PAH, TBT 

and heavy metals 

Solution: Construction of a confi ned disposal facility (CDF), dredging and placing of 

contaminated sediments in the CDF and binding of harmful substances by 

stabilisation 

Binder: Cement 80 kg/m 3 + fl y ash 40 kg/m 3 

Machinery: ALLU PM Power Mix 

Laboratory tests 

Stabilisation testing focused on reuse of industrial by-products in addition to cement. Stabilisation 

tests using binders containing cement, cement+silica or cement+fl y ash were performed. 

Necessary axial compression strength was estimated to be 100 kPa and chosen binder mixture 

gave strength of 250 kPa. Also the leaching tests were done to evaluate the leaching of contaminants 

from the stabilised material. 

Stabilisation tests were executed in the Ramboll Finland’s R&D laboratory. 

46 


CASES 

Monitoring 

An extensive monitoring programme was performedDuring and after the project. According to the 

results no elevated concentrations of metals or organic contaminants were found outside the 

CDF. Samples taken of the stabilised sediment had approximately the same strength as reached 

at the laboratory and results showed that the mixing of the binder in the fi eld had been successful. 

Costs 

Estimated cost for stabilisation of >100 000 m 3 of contaminated sediments: about 18 €/m 3 for 

dredging and transportation, 19-25 €/m 3 for stabilisation and 6-13 €/m 3 for establishing the 

CDF. This gives a total of about 50 €/m 3 . Direct stabilisation in the CDF is more cost-effi cient. 

Stabilisation 

Mixing was done fi rst in a separate basin and after the initial hardening the material was excavated 

and transported to the nearby CDF. As the CDF was fi lled the dike became less permeable 

and the fl ow of water reduced. When the fl ow stopped the mixing could be done in the CDF. 

The confi ned disposal facility and dredging 

The CDF with storage capacity of 80 000 m 3 was constructed by creating a water permeable 

dike to enclose the necessary area. Dredging was done with an enclosed bucket dredger, which 

reduced the spill of contaminant material and the amount of surplus water. 


47

FURTHER READING 

FURTHER READING 

ALLU Stabilisation System, Sales Manual in English, Spanish and Portugese. Free downloads in 

[http://www.allu.net/en/downloads.php] 

EuroSoilStab. Design guide soft soil stabilisation. Development of design and construction methods 

to stabilise soft organic soils. CT97-0351. (2002) 

Puumalainen N., Halkola H., Rantala K., Forsman J. & Hautalahti P.. Mass stabilisation and combined 

mass and column stabilisation in Kivikko area, Helsinki. NGM 2004, Ystad, Sweden, 19.- 

21.5.2004. (2004) 

Andersson, R., Carlsson, T., & Leppänen, M.. Hydraulic cement based binders for mass stabilisation 

of organic soils. Soft Ground Technology conference, The Netherlands. (2000) 

Laugersen J. et al. Stabilisation of contaminated sediments in Trondheim harbour – Special challenges. 

Proceedings of the International Conference on Deep Mixing – Best practice and Recent 

Advances, Deep Mixing’05. Stockholm, Sweden, May 23-25, 2005. Also other mass stabilisation 

articles in this publication. 

48

MASS STABILISATION MANUAL

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